The ribotype theory

In 1981 I proposed the first model of postchemical evolution with the ribotype theory on the origin of life, and with the concept of ribotype, a term that indicates all RNAs and ribonucleoproteins of any organic system (Barbieri, 1981). Since ribonucleoproteins are advanced compounds, the name rihosoids was introduced to indicate all molecules made of RNA, or RNA and peptides, and the ribotype was also defined as the collective of all rihosoids of an organic system. 

This is the novelty that characterised the first part of postchemical evolution, and had at least one important consequence the polymerising ribosoids allowed for the first time the production of peptides and small proteins inside the system, with endogenous syntheses, instead of importing these molecules from the outside. And this switch from exopoiesis to endopoiesis was an essential prerequisite for the development of a true autopoiesis. 

In addition to polymerising ribosoids, precellular systems were producing many other types of ribosoids, and, for statistical reasons, most of these were devoid of any metabolic value. A few, however, could have more interesting properties and behave, for example, like ribozymes or transfer-like RNAs. The first part of postchemical evolution was therefore a simple continuation of the metabolic processes of chemical evolution, with the difference that precellular systems were now carrying RNAs in their interior, which means that both the players and the rules of metabolism were slowly changing. 

Let us now come to the second part of postchemical evolution, the stage that was destined to lead to the origin of the first cells. It is in this stage that we must look for an answer to the problem that the replication paradigm has been unable to solve how did primitive systems manage to increase their complexity without being destroyed by error catastrophes The ribotype answer is based on three points. 

This then is the solution of the ribotype theory in order to avoid the error catastrophes in the journey toward exact replication, it was necessary to have high molecular weight protoribosomes, and the production of these ribosomes for an indefinite number of generations was possible, before exact replication, because ribosoids could achieve it with processes of self-assembly and quasi-replication. The development of high-molecular-weight protoribosomes took place during postchemical evolution, simply because all necessary conditions existed in that period, and the development could be realised with processes that were both natural and primitive. 

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The 1981 paper, furthermore, pointed out that the ribotype is not only independent from genotype and phenotype, but has a logical and a historical priority over them. According to the ribotype theory,... 

In 1981, the Journal of Theoretical Biology published The ribotype theory on the origin of life , a paper which proposed two novel ideas ... 

Barbieri, M. 1981. The ribotype theory of the origin of life. Journal of Theoretical Biology, 91,545-601. 

The origin-of-life scenario was instrumental for the new theory of the cell, because it led to the the conclusion that the ribotype had an evolutionary priority over genotype and phenotype. More precisely, the scenario described a precellular ribotype world (not to be confused with the RNA world) where some ribosoids could act as templates (ribogenotype), others as enzymes (ribophenotype), and others as polymerising ribosoids (ribotype) that were responsible for the growth and the quasi-replication of the ribonucleoprotein systems. 

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